With recent development of information communication technologies, a variety of wireless communication technologies have been developed. From among such technologies, WLAN is a technology that enables wireless Internet access at home, in businesses, or in specific service providing areas using a mobile terminal, such as a personal digital assistant (PDA), a laptop computer, or a portable multimedia player (PMP), based on radio frequency technology.
In order to overcome limited communication speed, which has been pointed out as a weak point of WLAN, technical standards have recently introduced a system capable of increasing the speed and reliability of a network while extending coverage of a wireless network. For example, IEEE 802.11n supports high throughput (HT) with a maximum data processing rate of 540 Mbps. In addition, Multiple Input Multiple Output (MIMO) technology, which employs multiple antennas for both a transmitter and a receiver in order to minimize transmission errors and optimize data rate, has been introduced.
Machine-to-machine (M2M) communication technology has been discussed as a next generation communication technology. A technical standard to support M2M communication in the IEEE 802.11 WLAN system is also under development as IEEE 802.11ah. In M2M communication, a scenario in which a small amount of data is occasionally communicated at a low speed in an environment having a large number of devices may be considered.
Communication in the WLAN system is performed on a medium shared by all devices. If the number of devices increases as in M2M communication, a channel access mechanism needs to be efficiently improved in order to reduce unnecessary power consumption and interference.